Data transmission method and apparatus

ABSTRACT

The present disclosure provides a data transmission method. A UE receives CSI-RS configuration signaling from a base station, measuring and reporting CSI according to the CSI-RS configuration signaling. The UE receives scheduling signaling from the base station, and receives downlink data according to the scheduling signaling. The method provides a way of measuring and feeding back CSI with reduced CSI-RS overhead. The method can configure DMRS ports in a flexible manner. Therefore, performances of MU-MIMO can be optimized.

PRIORITY

This application is a Continuation Application of application Ser. No.15/318,592 filed with the U.S. Patent and Trademark Office on Dec. 13,2016, which is a National Phase Entry of International Application No.PCT/KR2015/005888, filed on Jun. 11, 2015, and claims priority under 35U.S.C. § 119(a) to Patent Applications No. 201410443470.5 and201410265502.7, filed in the Chinese Intellectual Property Office onSep. 2, 2014 and Jun. 13, 2014, respectively, the contents of each ofwhich are incorporated herein by reference.

BACKGROUND 1. Field of the Disclosure

The present disclosure relates to wireless communication systems, andparticularly to a method and apparatus for configuring a channel stateinformation reference signal (CSI-RS), measuring channel stateinformation (CSI) and configuring a de-modulation reference signal(DMRS).

2. Description of the Related Art

In 3rd generation project partnership (3GPP) long term evolution (LTE)systems, each radio frame has a length of 10 ms and is equally dividedinto 10 subframes. As shown in FIG. 1, taking a frequency divisionduplexing (FDD) system as an example, each radio frame has a length of10 ms, and includes 10 subframes. Each subframe has a length of 1 ms,and is composed of two consecutive time slots, i.e., the k'th subframeincludes time slot 2 k and time slot 2 k+1, k=0, 1, . . . 9. Each timeslot has a length of 0.5 ms. A downlink transmission time interval (TTI)is defined in a subframe.

FIG. 2 is a schematic diagram illustrating a downlink subframe in an LTEsystem. As shown in FIG. 2, the preceding n orthogonal frequencydivision multiplexing (OFDM) symbols (n is 1, 2 or 3) are a downlinkcontrol channel region for transporting downlink control information ofusers. Downlink control channels include physical control formatindicator channel (PCFICH), physical hybrid automatic repeat request(HARM) indicator channel (PHICH) and physical downlink control channel(PDCCH). Remaining OFDM symbols are used for transporting physicaldownlink shared channel (PDSCH) and enhanced PDCCH (EPDCCH). Downlinkphysical channels are a collection of resource elements. A resourceelement (RE) is the smallest unit of time/frequency resources. RE is asubcarrier in frequency domain and an OFDM symbol in time domain. Thegranularity of physical resource allocation is physical resource block(PRB). A PRB includes 12 consecutive subcarriers in frequency domain,and corresponds to a time slot in time domain. Two PRBs within two timeslots on the same subcarriers in a subframe are referred to as a PRBpair. Different REs may have different usages, e.g., cell-specificreference signal (CRS), user-specific DMRS and channel state informationreference signal (CSI-RS). In a subframe, at most 40 REs may be used forCSI-RS transmission, and a base station may configure some or all of theREs to be used for CSI-RS transmission.

The number of CSI-RS ports may be configured to be 1, 2, 4, or 8according to the number of antennas deployed by the base station. Asshown in FIG. 3, when one or two CSI-RS ports are configured, CSI-RS istransported in two REs on the same subcarrier of two adjacent OFDMsymbols. When four CSI-RS ports are configured, CSI-RS is transported infour REs located in two adjacent OFDM symbols and two subcarriers. Wheneight CSI-RS ports are configured, CSI-RS is transported in eight REswhich are mapped onto four subcarriers of two adjacent OFDM symbols.

Information that needs to be specified may include the periodicity, thesubframe offset of CSI-RS and REs in a subframe, to identifytime/frequency resources on which the CSI-RS resources are mapped. Asshown in Table 1, CSI-RS subframe configuration is used for identifyingthe position in a subframe occupied by CSI-RS, i.e., indicating theperiodicity T_(CSI-RS) and the subframe offset Δ_(CSI-RS) of CSI-RS.Specifically, subframes for CSI-RS transmission satisfy(10n_(f)+└n_(s)/2┘−Δ_(CSI-RS))mod T_(CSI-RS)=0, where n_(f) is thesystem frame number, n_(s) is the time slot ID in a frame.

TABLE 1 Table 1: CSI RS subframe configuration CSI RS subframe CSI RSsubframe offset configuration CSI RS periodicity T_(CSI-RS) Δ_(CSI-RS)0-4 5 I_(CSI-RS)  5-14 10 I_(CSI-RS)-5 15-34 20 I_(CSI-RS)-15 35-74 40I_(CSI-RS)-35  75-154 80 I_(CSI-RS)-75

Table 2 shows REs onto which each CSI-RS configuration is mapped. In aPRB pair, REs corresponding to CSI-RS port 15 in CSI-RS configurationare determined by a two-tuple (k′,l′) according to the number of CSI-RSports, wherein k′ is a subcarrier index in the PRBs, l′ is an index ofan OFDM symbol in a time slot.

According to LTE standards, when one or two CSI-RS ports are configured,it may be regarded that the power of CSI-RS REs is normalized becauseeach antenna may transmit downlink signals in all REs in an OFDM symbol.When four CSI-RS ports are configured, preceding 2 CSI-RS ports and last2 CSI-RS ports are transmitted in different subcarriers respectively,which results in that the power of each CSI-RS port may be doubled,i.e., increased by 3 dB. When eight CSI-RS ports are configured, everytwo CSI-RS ports occupy one subcarrier, and do not transmit any signalin subcarriers of other CSI-RS ports, so that the power of each CSI-RSport may be quadrupled, i.e., increased by 6 dB.

Based on the above CSI-RS structure, conventional LTE systems maysupport downlink data transmission using 8 antenna ports. As shown inFIG. 4, antennas are generally deployed as a one-dimensional antennaarray in the horizontal direction, and are made to direct at differenthorizontal angles via beamforming. Terminals may be located at differentpositions in the vertical direction and may be at different distancesfrom the base station, and thus correspond to different vertical angles.In subsequent enhanced LTE systems, each cell may be configured with 16,32, 64 or more transmitting antennas to make use of the gain of spatialmultiplexing, increase cell throughput and reduce inter-userinterferences. As shown in FIG. 5, beamforming in the vertical directionand beamforming in the horizontal direction may be applied to atwo-dimensional antenna array to further reduce interference betweenterminals corresponding to different vertical direction angles andbetween terminals corresponding to different horizontal directionangles.

As such, cell throughput can be further increased, as shown in FIG. 6.

For systems configured with more than 8 physical antennas, e.g., thetwo-dimensional antenna array as shown in FIG. 5, proper methods areneeded to process multi-user multiple input multiple output (MU-MIMO)transmission and CSI measurement and feedback. The more physicalantennas configured, the narrower beams can be generated, and more userequipment (UEs) can be multiplexed using MU-MIMO techniques. Ato-be-solved problem is how to design DMRS to better support MU-MIMO. Ifeach physical transmitting antenna is configured with a CSI-RS port forCSI measurement, huge CSI-RS overhead may be generated. It is a problemto be solved that how to reduce the resources occupied by CSI-RS.Accordingly, a UE may measure the state of a radio channel according toCSI-RS configured, and feed CSI back. CSI information includes a rankindicator (RI), a channel quality indicator (CQI), a pre-coding matrixindicator (PMI) and etc. Another to-be-solved problem is how to measureand feedback CSI based on the CSI-RS structure adopted.

TABLE 2 Table 2: mapping table of CSI-RS configuration and two-tuples(k′, l′) the number of configured CSI-RS CSI-RS 1 or 2 4 8 configuration(k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 framestructure 0 (9, 5) 0 (9, 5) 0 (9, 5) 0 types 1 and 2 1 (11, 2)  1 (11,2)  1 (11, 2)  1 2 (9, 2) 1 (9, 2) 1 (9, 2) 1 3 (7, 2) 1 (7, 2) 1 (7, 2)1 4 (9, 5) 1 (9, 5) 1 (9, 5) 1 5 (8, 5) 0 (8, 5) 0 6 (10, 2)  1 (10, 2) 1 7 (8, 2) 1 (8, 2) 1 8 (6, 2) 1 (6, 2) 1 9 (8, 5) 1 (8, 5) 1 10 (3, 5)0 11 (2, 5) 0 12 (5, 2) 1 13 (4, 2) 1 15 (2, 2) 1 16 (1, 2) 1 17 (0, 2)1 18 (3, 5) 1 19 (2, 5) 1 applicable only to 20 (11, 1)  1 (11, 1)  1(11, 1)  1 frame structure 21 (9, 1) 1 (9, 1) 1 (9, 1) 1 type 2 22(7, 1) 1 (7, 1) 1 (7, 1) 1 23 (10, 1)  1 (10, 1)  1 24 (8, 1) 1 (8, 1) 125 (6, 1) 1 (6, 1) 1 26 (5, 1) 1 27 (4, 1) 1 28 (3, 1) 1 29 (2, 1) 1 30(1, 1) 1 31 (0, 1) 1

SUMMARY

The present disclosure relates to wireless communication systems, andparticularly to a method and apparatus for configuring CSI-RS, measuringCSI and configuring DMRS.

According to an aspect of the present disclosure, a method of a userequipment (UE) is provided, with the method including receivingconfiguration information related to a channel state information (CSI)process and measuring a channel state based on the configurationinformation. The CSI process is associated with at least two non-zeropower (NZP) channel state information reference signal (CSI-RS)resources, the UE assumes reference physical downlink shared channel(PDSCH) transmitted power corresponding to different NZP CSI-RSresources via higher layer signaling when measuring channel states inthe CSI based on the at least two NZP CSI-RS resources, and the assumedreference PDSCH transmitted power is based on P_(c) which is a ratio ofPDSCH energy per resource element (EPRE) to NZP CSI-RS energy per EPRE.

According to another aspect of the present disclosure, a user equipment(UE) for data processing is provided that includes a configurationsignaling receiving module configured to receive configurationinformation related to a channel state information (CSI) process from abase station (BS); and a CSI measuring and reporting module configuredto measure a channel state based on the configuration information, withthe CSI process being associated with at least two non-zero power (NZP)channel state information reference signal (CSI-RS) resources, with theUE assuming reference physical downlink shared channel (PDSCH)transmitted power corresponding to different NZP CSI-RS resources viahigher layer signaling when measuring channel states in the CSI based onthe at least two NZP CSI-RS resources, and with the reference PDSCHtransmitted power being based on P_(c) which is a ratio of PDSCH energyper resource element (EPRE) to NZP CSI-RS energy per (EPRE).

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating an LTE FDD frame;

FIG. 2 is a schematic diagram illustrating a subframe;

FIG. 3 is a schematic diagram illustrating CSI-RS;

FIG. 4 is a schematic diagram illustrating an antenna array;

FIG. 5 is a schematic diagram illustrating a two-dimensional antennaarray;

FIG. 6 is a schematic diagram illustrating beamforming;

FIG. 7 is a flowchart illustrating a method in accordance with anembodiment of the present disclosure;

FIG. 8 is a schematic diagram illustrating a first CSI-RS configuration;

FIG. 9 is a schematic diagram illustrating a second CSI-RSconfiguration;

FIG. 10 is a schematic diagram illustrating a third CSI-RSconfiguration;

FIG. 11 is a schematic diagram illustrating a fourth CSI-RSconfiguration;

FIG. 12 is a schematic diagram illustrating a fifth CSI-RSconfiguration;

FIG. 13 is a schematic diagram illustrating a sixth CSI-RSconfiguration;

FIG. 14 is a schematic diagram illustrating DMRS;

FIG. 15 is a schematic diagram illustrating modules of a datatransmitting apparatus in accordance with an embodiment of the presentdisclosure; and

FIG. 16 is a schematic diagram illustrating a seventh CSI-RSconfiguration.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Although ordinal numbers such as “first,” “second,” and so forth will beused to describe various components, those components are not limitedherein. The terms are used only for distinguishing one component fromanother component. For example, a first component may be referred to asa second component and likewise, a second component may also be referredto as a first component, without departing from the teaching of theinventive concept. The term “and/or” used herein includes any and allcombinations of one or more of the associated listed items.

The terminology used herein is for the purpose of describing variousembodiments only and is not intended to be limiting. As used herein, thesingular forms are intended to include the plural forms as well, unlessthe context clearly indicates otherwise. It will be further understoodthat the terms “comprises” and/or “has,” when used in thisspecification, specify the presence of a stated feature, number, step,operation, component, element, or combination thereof, but do notpreclude the presence or addition of one or more other features,numbers, steps, operations, components, elements, or combinationsthereof.

The terms used herein, including technical and scientific terms, havethe same meanings as terms that are generally understood by thoseskilled in the art, as long as the terms are not differently defined. Itshould be understood that terms defined in a generally-used dictionaryhave meanings coinciding with those of terms in the related technology.

According to various embodiments of the present disclosure, anelectronic device may include communication functionality. For example,an electronic device may be a smart phone, a tablet personal computer(PC), a mobile phone, a video phone, an e-book reader, a desktop PC, alaptop PC, a netbook PC, a personal digital assistant (PDA), a portablemultimedia player (PMP), an mp3 player, a mobile medical device, acamera, a wearable device (e.g., a head-mounted device (HMD), electronicclothes, electronic braces, an electronic necklace, an electronicappcessory, an electronic tattoo, or a smart watch), and/or the like.

According to various embodiments of the present disclosure, anelectronic device may be a smart home appliance with communicationfunctionality. A smart home appliance may be, for example, a television,a digital video disk (DVD) player, an audio, a refrigerator, an airconditioner, a vacuum cleaner, an oven, a microwave oven, a washer, adryer, an air purifier, a set-top box, a TV box (e.g., SamsungHomeSync™, Apple TV™, or Google TV™), a gaming console, an electronicdictionary, an electronic key, a camcorder, an electronic picture frame,and/or the like.

According to various embodiments of the present disclosure, anelectronic device may be a medical device (e.g., magnetic resonanceangiography (MRA) device, a magnetic resonance imaging (MRI) device,computed tomography (CT) device, an imaging device, or an ultrasonicdevice), a navigation device, a global positioning system (GPS)receiver, an event data recorder (EDR), a flight data recorder (FDR), anautomotive infotainment device, a naval electronic device (e.g., navalnavigation device, gyroscope, or compass), an avionic electronic device,a security device, an industrial or consumer robot, and/or the like.

According to various embodiments of the present disclosure, anelectronic device may be furniture, part of a building/structure, anelectronic board, electronic signature receiving device, a projector,various measuring devices (e.g., water, electricity, gas orelectro-magnetic wave measuring devices), and/or the like that includecommunication functionality.

According to various embodiments of the present disclosure, anelectronic device may be any combination of the foregoing devices. Inaddition, it will be apparent to one having ordinary skill in the artthat an electronic device according to various embodiments of thepresent disclosure is not limited to the foregoing devices.

A method and apparatus proposed in various embodiments of the presentdisclosure may be applied to various mobile communication systems suchas a Long Term Evolution (LTE) mobile communication system, anLTE-Advanced (LTE-A) mobile communication system, a High Speed DownlinkPacket Access (HSDPA) mobile communication system, a High Speed UplinkPacket Access (HSUPA) mobile communication system, a High Rate PacketData (HRPD) mobile communication system proposed in a 3rd GenerationProject Partnership 2 (3GPP2), a Wideband Code Division Multiple Access(WCDMA) mobile communication system proposed in the 3GPP2, a CodeDivision Multiple Access (CDMA) mobile communication system proposed inthe 3GPP2, an Institute of Electrical and Electronics Engineers (IEEE)802.16m communication system, an IEEE 802.11 communication system, anEvolved Packet System (EPS), a Mobile Internet Protocol (Mobile IP)system, a Wireless Universal Serial Bus (Wireless USB) system and/or thelike.

When the number of transmitting antennas configured in a base station isincreased, e.g., using a two-dimensional antenna array supporting 16,32, 64 or more transmitting antennas, it is necessary to modify thedesign of reference signals. A solution is to reduce the overhead ofCSI-RS while ensuring requirements of CSI feedback are met. Anothersolution is to make DMRS better support MU-MIMO transmission. FIG. 7 isa schematic diagram illustrating a method in accordance with theembodiments of the present disclosure. The method may include thefollowing procedures.

At block 701, a UE receives configuration signaling for CSI-RS from abase station, measures and reports CSI according to the CSI-RSconfiguration signaling.

The configuration signaling received by the UE may include:configuration information of a CSI process, e.g., configurationinformation of NZP CSI-RS for measuring channel characteristics,configuration information of CSI-IM resource for measuringinterferences. Configuration of CSI-IM resource may be implemented byconfiguring ZP CSI-RS. In an example, the configuration information ofthe CSI process may include configuration information of at least twoNZP CSI-RS.

In a system configured with relatively more physical antenna units, inorder to measure channels using NZP CSI-RS, a UE may be configured toreceive multiple NZP CSI-RS. Each NZP CSI-RS may be used for measuringsome of characteristics of the multi-antenna system. Therefore,measurement results of multiple NZP CSI-RS can be combined to obtaincomplete CSI information. Taking a two-dimensional antenna array as anexample, resources configured for one NZP CSI-RS may be used formeasuring characteristics of the antenna array in the horizontaldirection while resources configured for the other NZP CSI-RS may beused for measuring characteristics of the antenna array in the verticaldirection; the characteristics on the horizontal direction and thecharacteristics on the vertical direction may be combined to generatecomplete CSI information. Configuration information of each NZP CSI-RSmay specify a periodicity, a subframe offset and REs occupied in asubframe using the method defined in LTE Release 10, i.e., a NZP CSI-RSsupports at most 8 CSI-RS ports. Alternatively, the configurationinformation of each NZP CSI-RS may include CSI-RS resource of over 8CSI-RS ports, but in this case, modifications need to be made to the REmapping scheme.

Regarding the design of signaling mechanism, for a CSI process, multipleNZP CSI-RS included in the CSI process may be directly configured, or acollection of the multiple NZP CSI-RS may be re-defined as a combinedNZP CSI-RS. For the latter design, a CSI process by definition onlyincludes a combined NZP CSI-RS, but actually includes the multiple NZPCSI-RS. The following description takes directly configuring multipleNZP CSI-RS for a CSI process as an example. The following method can beapplied to situations where a collection of multiple NZP CSI-RS of a CSIprocess is re-defined as a combined NZP CSI-RS, and it can be applied toeach NZP CSI-RS in the combined NZP CSI-RS.

At block 702, the UE receives scheduling signaling from the basestation, and receives downlink data according to the schedulingsignaling.

The UE may receive scheduling signaling for scheduling downlink datatransmission, perform channel estimation based on the information on thenumber of layers and DMRS ports of data transmission in the schedulingsignaling, and decodes downlink data. More DMRS ports may be used forMU-MIMO to better support multi-user multiplexing.

The mechanism of the present disclosure is hereinafter described indetail with reference to the following examples.

Example 1

In a conventional LTE system, a CSI process refers to a NZP CSI-RSresource and a ZP CSI-RS resource serving as CSI-IM. In CSI measurement,NZP CSI-RS resource are used for channel measurement, CSI-MI resourceare used for interference measurement. Results of the channelmeasurement and the interference measurement are combined to generatethe complete CSI. In a system configured with relatively more physicalantenna units, e.g., using a two-dimensional antenna array supporting16, 32, 64 or more transmitting antenna units, channel measurementperformed through an NZP CSI-RS port configured for each physicaltransmitting power as in conventional systems may generate largeoverhead of NZP CSI-RS resource.

A method for reducing overhead includes configuring multiple NZP CSI-RSresources, and combining measurements of the multiple NZP CSI-RSresources to generate the CSI result. Each of the multiple NZP CSI-RSresources may include fewer NZP CSI-RS ports, so that total number ofNZP CSI-RS ports is less than the total number of physical antennaunits, which results in smaller total overhead of NZP CSI-RS resources.In an example, two NZP CSI-RS resources may be configured. A CSI processmay be configured with multiple NZP CSI-RS resources, and configurationinformation of the multiple NZP CSI-RS resources may be included inconfiguration information of a CSI process in configuration signalingsent by the base station. In an example, two NZP CSI-RS resources may beconfigured for a CSI process. As shown in FIG. 5, it is supposed atwo-dimensional antenna array is deployed in direction y and direction xand has respectively M rows and N columns. In an example, direction ymay be vertical, direction x may be horizontal. In other examples,directions x and y may be any two-dimensional directions. The followingtakes the vertical direction and the horizontal direction as an example.Various methods may be adopted to map each CSI-RS port of the multipleCSI-RS resources onto physical antenna units in the two-dimensionalantenna array. Methods for mapping CSI-RS resources respectively in thevertical direction and in the horizontal direction are described in thefollowing.

A co-polarized two-dimensional antenna array having M rows and N columnsmay be configured with one CSI-RS resource including M NZP CSI-RS ports,denoted as CSI-RS-0, for measuring vertical characteristics, and may beconfigured with another CSI-RS resource including N NZP CSI-RS ports,denoted as CSI-RS-1, for measuring horizontal characteristics. As shownin FIG. 8, supposing an antenna array has 8 rows and 8 columns, isconfigured with CSI-RS-0 including 8 ports in the vertical direction andCSI-RS-1 including 8 ports in the horizontal direction, channelcharacteristics obtained from measurement on CSI-RS-0 and CSI-RS-1 maybe combined to obtained the final CSI of the antenna array.

In FIG. 8, one NZP CSI-RS port in CSI-RS-0 and one NZP CSI-RS port inCSI-RS-1 are mapped onto the same antenna unit. The antenna unit isreferred to as a shared antenna unit. To avoid redundancy of NZP CSI-RSports, the shared antenna unit may only transmit one CSI-RS port asshown in FIG. 9, i.e., the CSI-RS port is shared by channel measurementin the horizontal direction and in the vertical direction. Accordingly,the UE receives NZP CSI-RS signal of one NZP CSI-RS port from the sharedantenna unit and uses the NZP CSI-RS signal for channel measurement inboth the horizontal direction and the vertical direction. The sharedantenna unit may be pre-set, e.g., in the left drawings in FIG. 8 andFIG. 9, the shared antenna unit correspond to port 0 of both CSI-RS-0and CSI-RS-1; in the right drawings in FIG. 8 and FIG. 9, the sharedantenna unit corresponds to port 3 of CSI-RS-0 and port 2 of CSI-RS-1.Alternatively, the shared antenna unit may be configured semi-staticallyby higher layer signaling, or indicated by physical layer signaling, ormay correspond to an antenna unit statically defined in the standard.

In FIG. 9, only M+N=15 CSI-RS ports actually need to be transmittedbecause the shared antenna unit occupies only one CSI-RS port. Thestructure of CSI-RS multiplexes two CSI-RS ports on two REs using aWalsh code having a length of 2, thus LTE systems are always capable ofsupporting an even number of CSI-RS ports. When the shared antenna unitoccupies only one CSI-RS port, the unoccupied CSI-RS port may be usedfor transmitting CSI-RS of another antenna unit to obtain measurementresults of plural antenna units. In an example as shown in FIG. 10, theadditional antenna unit may be an antenna unit having the longestdistance from both the antenna units of CSI-RS-0 and the antenna unitsof CSI-RS-1. The CSI-RS measurement result of the additional antennaunit may be used for revising the CSI measurement results based onCSI-RS-0 and CSI-RS-1. The UE may be informed of the additional antennaunit through signaling from the base station. Alternatively, theadditional antenna unit used for sending and receiving NZP CSI-RSsignals may be pre-determined. For example, the shared antenna unitoccupies only one NZP CSI-RS port in CSI-RS-0, and NZP CSI-RS of thenewly added antenna units may be transmitted via the NZP CSI-RS portcorresponding to the shared antenna unit in CSI-RS-1.

Alternatively, the two-dimensional antenna array may be divided intogroups, and NZP CSI-RS resources are allocated to each group of antennaunits on a diagonal line. For example, a two-dimensional antenna arraymay be equally divided into 4 groups of antenna units, each of whichincludes antenna units having M/2 rows and N/2 columns. For two groupsof antenna units on a diagonal line, NZP CSI-RS resources may beconfigured according to the above methods. For each group of antennaunits having 4 rows and 4 columns in FIG. 11, 4 CSI-RS ports may beconfigured according to a method similar to that as shown in FIG. 10 formeasuring vertical characteristics, and 4 CSI-RS ports may be configuredfor measuring horizontal characteristics. The shared antenna unitoccupies only one CSI-RS port, thus the other antenna unit may be usedfor transmitting CSI-RS of another port to enhance CSI measurementperformances. As shown in FIG. 12, each group of antenna units may adoptdifferent mapping methods for CSI-RS transmission. For an example, forthe group of antenna units at the lower left, the antenna units at theleft and at the bottom are used for transmitting CSI-RS; for the groupof antenna units at the upper right, the antenna units at the right andat the top are used for transmitting CSI-RS. The symmetrical structureis good for equalizing the effect of channel measurements and improvingmeasurement accuracy.

A cross-polarized two-dimensional antenna array having M rows and Ncolumns may be configured with one CSI-RS resource including M NZPCSI-RS ports, denoted as CSI-RS-0, for measuring verticalcharacteristics, and configured with another CSI-RS resource including2N NZP CSI-RS ports, denoted as CSI-RS-1, for measuring horizontalcharacteristics. For example, when N is smaller or equal to 4, CSI-RS-1includes not more than 8 CSI-RS ports. Alternatively, a cross-polarizedtwo-dimensional antenna array may be configured with a CSI-RS resourceincluding 2M CSI-RS ports, denoted as CSI-RS-0, for measuring verticalcharacteristics, and configured with another CSI-RS resource includinganother N CSI-RS ports, denoted as CSI-RS-1, for measuring horizontalcharacteristics. For example, when M is smaller or equal to 4, CSI-RS-0includes not more than 8 CSI-RS ports. Channel characteristics obtainedfrom measurement on CSI-RS-0 and CSI-RS-1 may be combined to obtain thefinal CSI information of the whole antenna array.

FIGS. 8-12 may still be used for illustrating the method of configuringCSI-RS ports in this situation. For example, it is supposed an antennaarray includes 8 rows and 4 columns and is configured with CSI-RS-0having 8 ports in the vertical direction and CSI-RS-1 having 8 ports inthe horizontal direction to measure the two polarization directions. Thefirst 4 columns and last 4 columns of antenna ports represent differentpolarization directions respectively. According to the method as shownin FIGS. 8-10, different numbers of CSI-RS ports are transmitted indifferent polarization directions. Regarding the method as shown in FIG.9 and FIG. 10, only one NZP CSI-RS port is used for the shared antennaunit, and the remaining CSI-RS port may be used for transmit NZP CSI-RSof another antenna unit in a polarized direction where there are lessNZP CSI-RS ports configured, so as to reduce the difference between thetwo polarized directions. In the method as shown in FIG. 9 and FIG. 10,the two NZP CSI-RS ports corresponding to the shared antenna unit areused for transmitting NZP CSI-RS for two antenna units in differentpolarized directions. Alternatively, a two-dimensional antenna array maybe divided into groups, e.g., the two-dimensional antenna array may beequally divided into 4 groups of antenna units according to the methodof FIG. 11 or FIG. 12. Because the first 4 columns and the last 4columns of antenna ports represent different polarization directions,the two polarization directions have the same number of transmittingCSI-RS ports. But each polarization direction does not have all of itsrows of antenna units transmitting CSI-RS.

For a cross-polarized two-dimensional antenna array of M rows and Ncolumns, a CSI-RS resource configured may include M NZP CSI-RS ports formeasuring characteristics in a first polarized direction, and is denotedas CSI-RS-0; and another CSI-RS resource configured may include N NZPCSI-RS ports for measuring characteristics in a second polarizeddirection, and is denoted as CSI-RS-1. FIG. 16 is a schematic diagramillustrates this method. But the M NZP CSI-RS ports in the firstpolarized direction may not necessarily correspond to antenna units inthe same column, and the N NZP CSI-RS ports in the second polarizeddirection may not necessarily correspond to antenna units in the samerow.

In addition, a cross-polarized two-dimensional antenna array having Mrows and N columns may be divided into two groups of antenna unitsaccording to the polarization directions. CSI-RS is configured for eachgroup of antenna units having the same polarization direction. In anexample, the two polarization directions may be configured with the samenumber of CSI-RS ports to equally measure channel characteristics of thetwo polarization directions. Each group of antenna units having the samepolarization direction includes M rows and N columns, the method asshown in FIGS. 8-12 may be adopted to allocate NZP CSI-RS, but methodsother than that of FIGS. 8-12 may also be applicable. For example, asshown in FIG. 13, supposing a cross-polarized two-dimensional antennaarray includes 8 rows and 4 columns, each group of 8-row 4-columnantenna units having the same polarization direction may be configuredwith 12 CSI-RS ports, thus a total of 24 antenna ports need to beconfigured. The CSI of the whole antenna array is measured by using the24 CSI-RS ports. As shown in the left drawing of FIG. 13, twopolarization directions may adopt the same pattern for mapping theCSI-RS ports. Alternatively, as shown in the right drawing of FIG. 13,the two polarization direction may adopt different patterns to map theCSI-RS ports. According to conventional resource allocation method whichsupport at most 8 CSI-RS ports, 3 groups of 8-port CSI-RS are requiredto transmit all CSI-RS ports. As shown in FIG. 13, different fillingsare used to represent different 8-port CSI-RS.

Example 2

In a system configured with relatively more physical antenna units,examples of the present disclosure provide a method for reducingoverhead. According to the method, multiple NZP CSI-RS resources areconfigured, and measurement results of the multiple NZP CSI-RS resourcesare combined to obtain the final CSI. The method of configuring multipleNZP CSI-RS resources is not restricted in the example.

In a conventional LTE system, a CSI process refers to a NZP CSI-RSresource and a ZP CSI-RS resource serving as CSI-IM. CSI-RS overhead canbe reduced by configuring multiple NZP CSI-RS resources. Accordingly, aCSI process may be defined as including multiple NZP CSI-RS resources.Although multiple NZP CSI-RS resources are used in channel measurement,but characteristics of interference signals are not dependent on themethod for measuring channels of CSI by using NZP CSI-RS resources.Therefore, interference measurement may still use only one CSI-IMresource. As such, in a system configured with relatively more physicalantenna units, supposing channel characteristics are measured byconfigured multiple NZP CSI-RS resources, a CSI process may beconfigured with multiple NZP CSI-RS resources and one multiple ZP CSI-RSresource serving as CSI-IM resource. In an example, a CSI process may beconfigured with two NZP CSI-RS resources and a CSI-IM resource.

In conventional LTE systems, for a CSI process configured with two CSIsubframe sets, e.g., in the situation where eIMTA is supported,definition of the CSI process has been extended to include a NZP CSI-RSresource and two ZP CSI-RS resources serving as CSI-IM resources. Inorder to obtain CSI feedback information for a CSI subframe set, REs oftwo CSI-IM resources in the CSI subframe set are used for measuringinterferences. Alternatively, a base station implements a method ofdetermining mapping between the two CSI-IM resources and the two CSIsubframe sets. Corresponding to the above method, in a system configuredwith relatively more physical antenna units, supposing channelcharacteristics are measured by configured multiple NZP CSI-RSresources, a CSI process may be configured with multiple NZP CSI-RSresources and two ZP CSI-RS resources serving as CSI-IM resources. In anexample, a CSI process may be configured with two NZP CSI-RS resourcesand two CSI-IM resources.

Example 3

In a system configured with relatively more physical antenna units,examples of the present disclosure provide a method for reducingoverhead. According to the method, two NZP CSI-RS resources areconfigured, and measurement results of the two NZP CSI-RS resources arecombined to obtain the final CSI. The method of configuring two NZPCSI-RS resources is not restricted in the example.

It is supposed a UE measures each NZP CSI-RS resource, and report CSIinformation of the NZP CSI-RS resource respectively. The CSI informationincludes at least PMI information obtained from measuring the NZP CSI-RSresource. With respect to RI and CQI, it is not restricted in thepresent disclosure whether a UE report RI and/or CQI for each NZP CSI-RSresource respectively or report a single RI and/or CQI obtained fromcombining the two CSI-RS resources. Denoting the PMI corresponding tothe k'th CSI-RS resource as PMI_(k), the UE may further report phaseinformation between each pair of PMI to enable the base station toobtain an optimal combined PMI for data transmission to the UE accordingto each individual PMI_(k). For example, supposing two CSI-RS resourcesare configured and a UE has reported PMI₀ and PMI₁ and each of whichindicates a precoding vector which has one layer, the UE may furtherfeed phase information back. The phase information is used for makingsignals of all the antenna units have the same phase to maximize thegain of beamforming during combination of PMI₀ and PMI₁ to generate thecombined PMI.

Example 4

In a conventional LTE system, a CSI process refers to a NZP CSI-RSresource and a ZP CSI-RS resource serving as CSI-IM resource. In CSImeasurement, NZP CSI-RS resource are used for channel measurement,CSI-MI resource are used for interference measurement. Results of thechannel measurement and the interference measurement are combined togenerate the CSI. The UE requires an assumption of a reference PDSCHtransmission power when measuring CSI to make the CSI informationobtained meet a certain target BLER value, e.g., 0.1. In conventionalstandards, the assumption of the reference PDSCH transmission power usedby the UE in CSI measurement is defined, i.e., a ratio of the energy perRE (EPRE) of the PDSCH to the EPRE of NZP CSI-RS, denoted as Pc. Inconventional LTE systems, EPRE of PDSCH on OFDM symbols that do notinclude CRS can be determined based on the Pc. Regarding the EPRE ofPDSCH on OFDM symbols including CRS, influence of a parameter PB is alsotaken into consideration according to conventional LTE methods.

In a system configured with relatively more physical antenna units,examples of the present disclosure provide a method for reducingoverhead. According to the method, multiple NZP CSI-RS resources areconfigured for a CSI process, and measurement results of the multipleNZP CSI-RS resources are combined to obtain the final CSI. The method ofconfiguring multiple NZP CSI-RS resources is not restricted in theexample.

For the multiple NZP CSI-RS resources configured to a CSI process,different NZP CSI-RS resources may have the same or different EPRE. Thepresent disclosure does not restrict the reason that makes different NZPCSI-RS resources have different EPRE. A possible reason is thatdifferent NZP CSI-RS resources have different numbers of CSI-RS ports,which results in that different NZP CSI-RS resources have differentenergy boostings. For example, denoting the normalized energy of eachantenna unit as P, supposing a first NZP CSI-RS resource includes 4ports and supposing each NZP CSI-RS port has an energy boosting of 3 dB,the energy of each RE carrying NZP CSI-RS is 4P; supposing a second NZPCSI-RS resource includes 8 ports and supposing each NZP CSI-RS port hasan energy boosting of 6 dB, the energy of each RE carrying NZP CSI-RS is8P, i.e., when the NZP CSI-RS has different number of antenna ports, REsof the NZP CSI-RS have different EPREs. In addition, different NZPCSI-RS resources may have different functions, and thus may havedifferent EPRE.

The multiple NZP CSI-RS resources of a CSI process may have differentEPRE, which affects the assumption of the reference PDSCH transmissionpower when the UE measures CSI based on each NZP CSI-RS resource. The UEmay use the same reference PDSCH transmission power in channel statemeasurement using different NZP CSI-RS resources. Alternatively, thebase station may set different reference PDSCH transmission power fordifferent NZP CSI-RS resources. Six examples of the method of thepresent disclosure is described as follows.

According to a first method of setting a reference PDSCH transmissionpower, N assumptions of the reference PDSCH transmission power may beset via higher layer signaling for a CSI process configured with N NZPCSI-RS resources, denoted as P_(c) ^((k)), k=0, 1, . . . N−1. Whenmeasuring CSI using the k'th NZP CSI-RS resource, the UE may determinethe assumption of the reference PDSCH transmission power according toP_(c) ^((k)). The referent PDSCH transmission power obtained by usingthe P_(c) ^((k)) may be the same for the N NZP CSI-RS resources inchannel state measurement of the UE. Alternatively, the base station mayalso set the P_(c) ^((k)) such that the transmission power of thereference PDSCH is different for different NZP CSI-RS resources.

According to a second method for setting the reference PDSCHtransmission power, an assumption of a reference PDSCH transmissionpower Pc may be configured via higher layer signaling for one of themultiple NZP CSI-RS resources configured to a CSI process, and therebythe reference PDSCH transmission power when CSI is measured using theNZP CSI-RS is configured. The UE may obtain assumption(s) of thereference PDSCH transmission power used in measuring CSI using other NZPCSI-RS resource(s) according to differences in the number of ports ofthe different NZP CSI-RS resources. For example, the differences in thenumber of CSI-RS ports may be compensated to obtain the same referencePDSCH transmission power for channel state measurement using each NZPCSI-RS resource. The NZP CSI-RS resource to which the Pc is configuredmay be specified in the higher layer signaling, i.e., the higher layersignaling may specify the index of the NZP CSI-RS resource correspondingto the Pc. Alternatively, it may be defined that the Pc is configuredfor a NZP CSI-RS resource that has a preset index, e.g., the index maybe 0 or 1, and thus there is no need to specify the index in the higherlayer signaling. The NZP CSI-RS resource to which the Pc is configuredis herein referred to as reference NZP CSI-RS resource.

Denoting the number of ports of the reference NZP CSI-RS resource is p₀,and supposing the number of ports of another NZP CSI-RS resource isp_(k), p₀ and p_(k) are generally exponentiation values of 2, when theUE measures CSI using the k'th NZP CSI-RS resource, the assumption ofthe reference PDSCH transmission power P_(c) ^((k)), i.e., the ratio ofEPRE of the reference PDSCH to the EPRE of the k'th NZP CSI-RS, may beobtained according to the following formula:

$P_{c}^{(k)} = \left\{ \begin{matrix}P_{c} & {{p_{0} = 1},{p_{k} = 1}} \\{\frac{p_{0}}{2} \cdot P_{c}} & {{p_{0} \geq 2},{p_{k} = 1}} \\{\frac{2}{p_{k}} \cdot P_{c}} & {{p_{0} = 1},{p_{k} \geq 2}} \\{\frac{p_{0}}{p_{k}} \cdot P_{c}} & {{p_{0} \geq 2},{p_{k} \geq 2}}\end{matrix} \right.$

According to a third method for configuring the reference PDSCHtransmission power, an assumption of a reference PDSCH transmissionpower Pc may be configured via higher layer signaling for one ofmultiple NZP CSI-RS resources configured for a CSI process. As such, thereference PDSCH transmission power used in CSI measurement using the NZPCSI-RS resource is configured. The UE may use the same reference PDSCHtransmission power in CSI measurement using each NZP CSI-RS resource.The NZP CSI-RS resource to which the Pc is configured may be specifiedin the higher layer signaling, i.e., the higher layer signaling mayspecify the index of the NZP CSI-RS resource corresponding to the Pc.Alternatively, it may be defined that the Pc is configured for a NZPCSI-RS resource that has a preset index, e.g., the index may be 0 or 1,and thus there is no need to specify the index in the higher layersignaling. The NZP CSI-RS resource to which the Pc is configured isherein referred to as reference NZP CSI-RS resource.

In an example, the UE may obtain assumption(s) of the reference PDSCHtransmission power used in CSI measurement using each of the other NZPCSI-RS resource(s) based on the Pc configured for the reference NZPCSI-RS resource and differences in the number of ports of different NZPCSI-RS resources under the condition of using the same reference PDSCHtransmission power for each NZP CSI-RS. Similar to the above secondmethod of configuring the reference PDSCH transmission power, denotingthe number of ports of the referent NZP CSI-RS resource is p₀, supposingthe number of ports of anther NZP CSI-RS resource is p_(k), p₀ and p_(k)are generally exponentiations of 2, when the UE measures CSI using thek'th NZP CSI-RS resource, the assumption of the reference PDSCHtransmission power P_(c) ^((k)), i.e., the ratio of EPRE of thereference PDSCH to EPRE of the k'th NZP CSI-RS resource, may be obtainedby using the following formula:

$P_{c}^{(k)} = \left\{ \begin{matrix}P_{c} & {{p_{0} = 1},{p_{k} = 1}} \\{\frac{p_{0}}{2} \cdot P_{c}} & {{p_{0} \geq 2},{p_{k} = 1}} \\{\frac{2}{p_{k}} \cdot P_{c}} & {{p_{0} = 1},{p_{k} \geq 2}} \\{\frac{p_{0}}{p_{k}} \cdot P_{c}} & {{p_{0} \geq 2},{p_{k} \geq 2}}\end{matrix} \right.$

According to a fourth method of configuring a reference PDSCHtransmission power, for a CSI process configured with N NZP CSI-RSresources, an assumption of a reference PDSCH transmission power Pc maybe configured and applied to all N NZP CSI-RS resources. That is, EPREof the reference PDSCH for each NZP CSI-RS may be obtained by using thePc and the EPRE of the NZP CSI-RS. According to this method, the basestation functions to ensure that applying the same Pc to all the N NZPCSI-RS resources can meet the performance requirements of CSImeasurement. If the N NZP CSI-RS resources have different EPRE, thereference PDSCH transmission powers of different NZP CSI-RS are alsodifferent. Alternatively, even if the N NZP CSI-RS resources havedifferent number of ports, the base station may still configure the NNZP CSI-RS resources to use identical EPRE so that sharing the same Pcmay still result in the UE using the same reference PDSCH transmissionpower in channel state measurement based on each of N NZP CSI-RSresources. In this example, it is supposed that different NZP CSI-RSresources have different number of ports, and the NZP CSI-RS ports ofthe different NZP CSI-RS resources have different energy boostings.

According to a fifth method of configuring a reference PDSCHtransmission power, the UE may use a preset Pc value, e.g., 0 dB, in CSImeasurement using some of the multiple NZP CSI-RS resources of a CSIprocess. While the parameter Pc used in determining the reference PDSCHtransmission power for other NZP CSI-RS resources may be configuredusing the above 4 methods. In an example, supposing a CSI processincludes two NZP CSI-RS resources respectively denoted as CSI-RS-A andCSI-RS-B, the UE may first measure CSI-RS-A and report measured PMI_(A)to the base station. The base station precodes CSI-RS-B according to thePMI_(A) and transmits the CSI-RS-B. The UE performs measurement based onthe CSI-RS-B and feeds back measured CSI. The CSI-RS-A is used forobtaining the PMI_(A) for precoding the CSI-RS-B, and is not directlyrelated to transmission of the reference PDSCH. Thus, the UE may measurePMI_(A) assuming the ratio of the power of PDSCH signals to the EPRE ofthe CSI-RS-A is 1. The Pc configured via higher layer signaling is usedonly for determining the reference PDSCH transmission power in CSImeasurement based on the CSI-RS-B.

According to the sixth method of configuring a reference PDSCHtransmission power, according to usages of the multiple NZP CSI-RSresources, the UE may perform CSI measurement based on some of themultiple NZP CSI-RS resources without additional assumptions of signalpowers, and obtain the parameter Pc for use in determining the referencePDSCH transmission power for other NZP CSI-RS resources by using theabove 4 methods. In an example, supposing a CSI process includes two NZPCSI-RS resources respectively denoted as CSI-RS-A and CSI-RS-B, the UEmay report PMI_(A) through measurement based on the CSI-RS-A to the basestation, but does not feed back other information such as CQI. The basestation precodes the CSI-RS-B using the PMI_(A) and transmits theCSI-RS-B. The UE performs measurement based on the CSI-RS-B and feedsback measured CSI. Regarding CSI-RS-A, the UE may directly obtainPMI_(A) using the CSI-RS-A in measurement without additional assumptionof a signal power because there is no need to feed back otherinformation such as CQI. The Pc configured via the higher layersignaling is used only in determining the reference PDSCH transmissionpower for CSI measurement based on the CSI-RS-B.

According to the above four examples, a CSI process is configured withmultiple NZP CSI-RS resources for CSI measurement to obtain complete CSIinformation and reduce the overhead of NZP CSI-RS resources. Thefollowing example illustrates a design of DMRS transmission to bettersupport MU-MIMO.

Example 5

FIG. 14 is a schematic diagram illustrating DMRS mappings ofconventional LTE systems. When MU-MIMO needs to be supported,conventional LTE systems only support multiplexing the DMRS of multipleUEs in 12 REs (e.g., REs filled with grids in FIG. 14). In an example, aWalsh code having a length of 2 is adopted for time-expanded, DMRS ports7 and 8 are used for DMRS transmission, and different n_(SCID) areconfigured to generate two quasi-orthogonal DMRS sequences. DMRSsequences generated using the same n_(SCID) for DMRS ports are fullyorthogonal, while DMRS sequences generated using different n_(SCID) arequasi-orthogonal.

In a system configured with relatively more physical antenna units,e.g., with 16, 32, 64 or more transmitting antenna units, the increasein the number of antenna units enables better support of MU-MIMO. Butconventional LTE methods only support two fully orthogonal DMRS ports,thus the multiplexing PDSCH of multiple UE on the same resources havelimited performances. In an example, two methods to extend DMRS portsare provided. Scheduling signaling sent by a base station to a UEspecifies DMRS ports allocated to the UE. The UE receives DMRS signals,performs channel estimation and downlink data processing using the DMRSports. The DMRS ports allocated to the UE are not limited to fullyorthogonal DMRS ports supporting MU-MIMO as in conventional LTE methods,but include other ports. The following are a few examples.

A method increases REs used for DMRS to better support orthogonal DMRSports. For example, as shown in FIG. 14, all of 24 DMRS REs are usedDMRS transmission for MU-MIMO support, i.e., DMRS ports 7-10 defined inconventional LTE standards are made to support MU-MIMO. But according tothis method, the number of REs actually available for PDSCH transmissionis reduced by 12, thus performances of PDSCH transmission may beaffected.

In order to reduce DMRS overhead, when DMRS is only transmitting in theRE collection of port 7, the base station may instruct the UE to receivePDSCH from the RE collection of port 9. In an example, denoting thenumber of RE collections occupied by DMRS is N_(DMRS), the schedulingsignal may include the N_(DMRS) to specify the RE collections actuallyoccupied by DMRS. A N_(DMRS) having a value of 1 indicates DMRS is onlytransmitted in the RE collection of port 7, and a N_(DMRS) having avalue of 2 indicates DMRS is transmitted in the RE collections of port 7and port 9. Table 3 is an example of this method. When a single codewordis transmitted or re-transmitted in a single layer, if N_(DMRS) equals1, indication information is required to specify DMRS port 7 or 8 andspecify whether n_(SCID) equals 0 or 1, i.e., there are 4 possibilitiesthat need to be specified; if N_(DMRS) equals 2, indication informationis required to specify one of DMRS ports 7-10 and specify whethern_(SCID) equals 0 or 1, i.e., there are 8 possibilities that need to bespecified. When a codeword occupying 2 layers in initially transmissionis re-transmitted, indication information is required to specify whetherN_(DMRS) equals 1 or 2 because data of other UE(s) may be involved inthe MU-MIMO transmission, and accordingly, there are 2 possibilitiesthat need to be specified, and n_(SCID) equals 0 by default. When acodeword occupying 3 or 4 layers in initial transmission isre-transmitted, there are 2 possibilities that need to be specified, andn_(SCID) equals 0 by default. Regarding transmission of two codewords,when two layers are allocated to the UE, if N_(DMRS) equals 1, ports 7and 8 may be used, and indication information is required to specifywhether n_(SCID) equals 0 or 1, so there are two possibilities; ifN_(DMRS) equals 2, ports 7 and 8 or ports 9 and 10 may be used, andn_(SCID) may be 0 or 1, thus, there are 4 possibilities that need to bespecified; when more than 3 layers are allocated to the UE, only SU-MIMOis supported, thus there are 6 possibilities, i.e., the total number oflayers may be 3, 4, 5, 6, 7, 8, and n_(SCID) equals 0 by default.

TABLE 3 Table 3: method of specifying the number of layers allocated andDMRS ports codeword 0 available, codeword 1 unavailable both codewordsavailable Value Information Value Information 0 1 layer, port 7,n_(SCID) = 0, N_(DMRS) = 1 0 2 layers, port 8, n_(SCID) = 0, N_(DMRS) =1 1 1 layer, port 7, n_(SCID) = 1, N_(DMRS) = 1 1 2 layers, ports 7-8,n_(SCID) = 1, N_(DMRS) = 1 2 1 layer, port 8, n_(SCID) = 0, N_(DMRS) = 12 2 layers, ports 7-8, n_(SCID) = 0, N_(DMRS) = 2 3 1 layer, port 8,n_(SCID) = 1, N_(DMRS) = 1 3 2 layers, ports 7-8, n_(SCID) = 1, N_(DMRS)= 2 4 1 layer, port 7, n_(SCID) = 0, N_(DMRS) = 2 4 2 layers, ports 9and 10, n_(SCID) = 0, N_(DMRS) = 2 5 1 layer, port 7, n_(SCID) = 1,N_(DMRS) = 2 5 2 layers, ports 9 and 10, n_(SCID) = 1, N_(DMRS) = 2 6 1layer, port 8, n_(SCID) = 0, N_(DMRS) = 2 6 3 layers, ports 7-9 7 1layer, port 8, n_(SCID) = 1, N_(DMRS) = 2 7 4 layers, ports 7-10 8 1layer, port 9, n_(SCID) = 0, N_(DMRS) = 2 8 5 layers, ports 7-11 9 1layer, port 9, n_(SCID) = 1, N_(DMRS) = 2 9 6 layers, ports 7-12 10 1layer, port 10, n_(SCID) = 0, 10 7 layers, ports 7-13 N_(DMRS) = 2 11 1layer, port 10, n_(SCID) = 1, N_(DMRS) = 2 11 8 layers, ports 7-14 12 2layers, ports 7-8, n_(SCID) = 0, 12 reserved N_(DMRS) = 1 13 2 layers,ports 7-8, n_(SCID) = 0, 13 reserved N_(DMRS) = 2 14 3 layers, ports 7-914 reserved 15 4 layers, ports 7-10 15 reserved

According to another method, the number of REs for DMRS is notincreased, i.e., the 12 REs filled with grids as shown in FIG. 14 arestill used, the length of a Walsh code for time-expanded is increased tosupport MU-MIMO transmission of DMRS so as to multiplex more orthogonalDMRS.

A time-expanded code having a length of 4 is used on the 12 DMRS REs forMU-MIMO, and 4 DMRS ports that can be used are 7, 8, 11 and 13. Table 4is the time-expanded codes to which the 4 ports are mapped. Therelationships regarding orthogonality between the 4 time-expanded codesare different. For example, the time-expanded code of port 7 has thebest orthogonality with the time-expanded code of port 8, but has theworst orthogonality with the time-expanded code of port 11. Inconventional LTE standards, when dual-layer transmission is supported,port 7 and port 8 are allocated to a UE, i.e., allocating twotime-expanded codes that have the best orthogonality of the 4time-expanded codes as shown in Table 4 to the same UE. In order to addflexibility to DMRS allocation of a base station, during DMRSallocation, the two ports that have the best orthogonality in the 4 DMRSports may be allocated to different layers of the same UE to reduceinterference between the two layers of the UE, or may be allocated todifferent UEs to reduce interference between the UEs.

TABLE 4 Table 4: time-expanded codes of DMRS ports DMRS portstime-expanded code 7 [+1 +1 +1 +1] 8 [+1 −1 +1 −1] 11 [+1 +1 −1 −1] 13[+1 −1 −1 +1]

Table 5 illustrates a method for specifying the number of layersallocated and DMRS ports in accordance with an example of the presentdisclosure. When a single codeword is transmitted or re-transmittedusing a single layer, indication information is required to specify oneof DMRS ports 7, 8, 11, 13 and specify whether n_(SCID) is 0 or 1, thusthere are 8 possibilities that need to be specified. When a singlecodeword is n_(SCID)-transmitted and the number of layers in initialtransmission is larger than or equal to 2, additional indicationinformation is required to specify whether the number of layers is 2, 3,or 4, i.e., there are 3 possibilities, and n_(SCID) is 0 by default.Regarding transmission of two codewords, when two layers are allocatedto the UE, ports 7 and 8, or ports 11 and 13, or ports 7 and 11, orports 8 and 13 may be used, and n_(SCID) may be 0 or 1, thus, there are8 possibilities that need to be specified; when more than 3 layers areallocated to the UE, only SU-MIMO is supported, thus there are 6possibilities, i.e., the total number of layers may be 3, 4, 5, 6, 7, 8,and n_(SCID) equals 0 by default.

TABLE 5 Table 5: method of specifying the number of allocated layers andDMRS ports codeword 0 available, codeword 1 unavailable both codewordsavailable Value Information Value Information 0 1 layer, port 7,n_(SCID) = 0 0 2 layers, ports 7-8, n_(SCID) = 0 1 1 layer, port 7,n_(SCID) = 1 1 2 layers, ports 7-8, n_(SCID) = 1 2 1 layer, port 8,n_(SCID) = 0 2 2 layers, ports 11 and 13, n_(SCID) = 0 3 1 layer, port8, n_(SCID) = 1 3 2 layers, ports 11 and 13, n_(SCID) = 1 4 1 layer,port 11, n_(SCID) = 0 4 2 layers, ports 7 and 11, n_(SCID) = 0 5 1layer, port 11, n_(SCID) = 1 5 2 layers, ports 7 and 11, n_(SCID) = 1 61 layer, port 13, n_(SCID) = 0 6 2 layers, ports 8 and 13, n_(SCID) = 07 1 layer, port 13, n_(SCID) = 1 7 2 layers, ports 8 and 13, n_(SCID) =1 8 2 layers, ports 7-8 8 3 layers, ports 7-9 9 3 layers, ports 7-9 9 4layers, ports 7-10 10 4 layers, ports 7-10 10 5 layers, ports 7-11 11reserved 11 6 layers, ports 7-12 12 reserved 12 7 layers, ports 7-13 13reserved 13 8 layers, ports 7-14 14 reserved 14 reserved 15 reserved 15reserved

According to the method of Table 5, the UE may perform channelestimation without the need of any information on the length of thetime-expanded code, or the UE may perform channel estimation alwaysregarding the length of the time-expanded code is 4.

The length of the time-expanded code may be specified along with thenumber of layers and DMRS ports because a time-expanded code whoselength is 2 has better despreading performances than a time-expandedcode whose length is 4, so that the UE may use the length of thetime-expanded code in improving channel estimation results. The lengthof the time-expanded code is denoted as Locc. Table 6 is an example ofthis method. When a single codeword is transmitted or re-transmitted ina single layer, if Locc equals 2, indication information is required tospecify DMRS port 7 or 8 and specify whether n_(SCID) equals 0 or 2,i.e., there are 4 possibilities that need to be specified; if Loccequals 4, indication information is required to specify one of DMRSports 7, 8, 11 and 13 and specify whether n_(SCID) equals 0 or 1, i.e.,there are 8 possibilities that need to be specified. When a codewordoccupying 2 layers in initially transmission is re-transmitted, furtherindication information is required to specify whether Locc equals 2 or 4because data of other UE(s) may be involved in the MU-MIMO transmission,and accordingly, there are 2 possibilities that need to be specified,and n_(SCID) equals 0 by default. When a codeword occupying 3 or layersin initial transmission is re-transmitted, there are 2 possibilitiesthat need to be specified, and n_(SCID) equals 0 by default. When twocodewords are transmitted, if the number of layers allocated to the UEis 2, if Locc=2, ports 7 and 8 may be used, n_(SCID) may be 0 or 1,i.e., there are 2 possibilities that need to be specified; if Locc=4,ports 7 and 8, or ports 11 and 13 may be used, n_(SCID) may be 0 or 1,i.e., there are 4 possibilities that need to be specified; if the numberof layers allocated to the UE is larger than or equal to 3, only SU-MIMOis supported, and therefore 6 possibilities need to be specified, i.e.,the total number of layers may be 3, 4, 5, 6, 7 and 8, n_(SCID) is 0 bydefault.

TABLE 6 Table 6: method of specifying the number of allocated layers andDMRS ports codeword 0 available, codeword 1 unavailable both codewordsavailable Value Information Value Information 0 1 layer, port 7,n_(SCID) = 0, 0 2 layers, ports 7-8, n_(SCID) = 0, L_(OCC) = 2 L_(OCC) =2 1 1 layer, port 7, n_(SCID) = 1, 1 2 layers, ports 7-8, n_(SCID) = 1,L_(OCC) = 2 L_(OCC) = 2 2 1 layer, port 8, n_(SCID) = 0, 2 2 layers,ports 7-8, n_(SCID) = 0, L_(OCC) = 2 L_(OCC) = 4 3 1 layer, port 8,n_(SCID) = 1, 3 2 layers, ports 7-8, n_(SCID) = 1, L_(OCC) = 2 L_(OCC) =4 4 1 layer, port 7, n_(SCID) = 0, 4 2 layers, ports 11 and 13, n_(SCID)= 0, L_(OCC) = 4 L_(OCC) = 4 5 1 layer, port 7, n_(SCID) = 1, 5 2layers, ports 11 and 13, n_(SCID) = 1, L_(OCC) = 4 L_(OCC) = 4 6 1layer, port 8, n_(SCID) = 0, L_(OCC) = 4 6 3 layers, ports 7-9 7 1layer, port 8, n_(SCID) = 1, L_(OCC) = 4 7 4 layers, ports 7-10 8 1layer, port 11, n_(SCID) = 0, L_(OCC) = 4 8 5 layers, ports 7-11 9 1layer, port 11, n_(SCID) = 1, L_(OCC) = 4 9 6 layers, ports 7-12 10 1layer, port 13, n_(SCID) = 0, L_(OCC) = 4 10 7 layers, ports 7-13 11 1layer, port 13, n_(SCID) = 1, L_(OCC) = 4 11 8 layers, ports 7-14 12 2layers, ports 7-8, n_(SCID) = 0, 12 reserved L_(OCC) = 2 13 2 layers,ports 7-8, n_(SCID) = 0, 13 reserved L_(OCC) = 4 14 3 layers, ports 7-914 reserved 15 4 layers, ports 7-10 15 reserved

A method as shown in Table 7 may be obtained by combining the methods ofTable 5 and Table 6. According to the method, transmission of dataoccupying 2 layers uses ports 7 and 8, ports 11 and 13, ports 7 and 11,or ports 8 and 13, and Locc is specified.

TABLE 7 Table 7: method of specifying the number of allocated layers andDMRS ports codeword 0 available, codeword 1 unavailable both codewordsavailable Value Information Value Information 0 1 layer, port 7,n_(SCID) = 0, 0 2 layers, ports 7-8, n_(SCID) = 0, L_(OCC) = 2 L_(OCC) =2 1 1 layer, port 7, n_(SCID) = 1, L_(OCC) = 2 1 2 layers, ports 7-8,n_(SCID) = 1, L_(OCC) = 2 2 1 layer, port 8, n_(SCID) = 0, L_(OCC) = 2 22 layers, ports 7-8, n_(SCID) = 0, L_(OCC) = 4 3 1 layer, port 8,n_(SCID) = 1, L_(OCC) = 2 3 2 layers, ports 7-8, n_(SCID) = 1, L_(OCC) =4 4 1 layer, port 7, n_(SCID) = 0, L_(OCC) = 4 4 2 layers, ports 11 and13, n_(SCID) = 0, L_(OCC) = 4 5 1 layer, port 7, n_(SCID) = 1, L_(OCC) =4 5 2 layers, ports 11 and 13, n_(SCID) = 1, L_(OCC) = 4 6 1 layer, port8, n_(SCID) = 0, L_(OCC) = 4 6 2 layers, ports 7 and 11, n_(SCID) = 0,L_(OCC) = 4 7 1 layer, port 8, n_(SCID) = 1, L_(OCC) = 4 7 2 layers,ports 7 and 11, n_(SCID) = 1, L_(OCC) = 4 8 1 layer, port 11, n_(SCID) =0, L_(OCC) = 4 8 2 layers, ports 8 and 13, n_(SCID) = 0, L_(OCC) = 4 9 1layer, port 11, n_(SCID) = 1, L_(OCC) = 4 9 2 layers, ports 8 and 13,n_(SCID) = 1, L_(OCC) = 4 10 1 layer, port 13, n_(SCID) = 0, L_(OCC) = 410 3 layers, ports 7-9 11 1 layer, port 13, n_(SCID) = 1, L_(OCC) = 4 114 layers, ports 7-10 12 2 layers, ports 7-8, n_(SCID) = 0, 12 5 layers,ports 7-11 L_(OCC) = 2 13 2 layers, ports 7-8, n_(SCID) = 0, 13 6layers, ports 7-12 L_(OCC) = 4 14 3 layers, ports 7-9 14 7 layers, ports7-13 15 4 layers, ports 7-10 15 8 layers, ports 7-14

The method of example five can support more DMRS ports being used forMU-MIMO.

The above are several examples of the data transmission method of thepresent disclosure. The present disclosure also provides a datatransmission apparatus configured to implement the above datatransmission method. FIG. 15 is a schematic diagram illustrating modulesof a data transmitting apparatus in accordance with an embodiment of thepresent disclosure. As shown in FIG. 15, the data transmission apparatusmay include: a configuration signaling receiving module, a CSI measuringand reporting module, a scheduling signaling receiving module and adownlink data receiving module.

The configuration signaling receiving module is configured to receiveconfiguration signaling for CSI-RS sent by a base station. The CSImeasuring and reporting module is configured to measure and report CSIaccording to the configuration signaling for CSI-RS. The schedulingsignaling receiving module is configured to receive scheduling signalingsent by the base station. The downlink data receiving module isconfigured to receive downlink data according to the schedulingsignaling.

In an example, configuration information of a CSI process in theconfiguration signaling received by the configuration signalingreceiving module may include configuration information of at least twoNZP CSI-RS resources. The CSI measuring and reporting module may receiveNZP CSI-RS signals according to configuration information of all NZPCSI-RS resources of the CSI process, and combine measurement results ofall NZP CSI-RS signals received in a CSI process to obtain the CSIinformation.

The scheduling signaling received by the scheduling signaling receivingmodule may include information of DMRS ports allocated to the UE, thenumber of data transmission layers and the number of RE collectionsactually occupied by DMRS denoted as N_(DMRS). The downlink datareceiving module may receive DMRS signals according to the DMRS portsallocated and the number of data transmission layers in the schedulingsignaling. DMRS 7-10 are used for supporting MU-MIMO transmission ofDMRS signals. When N_(DMRS) indicates DMRS signals are only transmittedin the RE collection of port 7, the downlink data receiving module mayreceive PDSCH on the RE collection of port 9.

Alternatively, the scheduling signaling received by the schedulingsignaling receiving module includes information of DMRS ports allocatedto the UE and the number of data transmission layers. The length of atime-expanded Walsh code is added to support MU-MIMO transmission. DMRSports allocated to the UE are DMRS ports that have the bestorthogonality in all of DMRS ports that support MU-MIMO. Alternatively,DMRS ports that have the best orthogonality in all of DMRS ports thatsupport MU-MIMO are allocated to different UEs. In an example, thescheduling signaling may also include the length Locc of thetime-expanded code corresponding to the DMRS port allocated to the UE.

Certain aspects of the present disclosure may also be embodied ascomputer readable code on a non-transitory computer readable recordingmedium. A non-transitory computer readable recording medium is any datastorage device that can store data, which can be thereafter read by acomputer system. Examples of the non-transitory computer readablerecording medium include read only memory (ROM), random access memory(RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storagedevices, and carrier waves (such as data transmission through theInternet). The non-transitory computer readable recording medium canalso be distributed over network coupled computer systems so that thecomputer readable code is stored and executed in a distributed fashion.In addition, functional programs, code, and code segments foraccomplishing the present disclosure can be easily construed byprogrammers skilled in the art to which the present disclosure pertains.

It can be appreciated that a method and apparatus according to anembodiment of the present disclosure may be implemented by hardware,software and/or a combination thereof. The software may be stored in anon-volatile storage, for example, an erasable or re-writable ROM, amemory, for example, a RAM, a memory chip, a memory device, or a memoryintegrated circuit (IC), or an optically or magnetically recordablenon-transitory machine-readable (e.g., computer-readable), storagemedium (e.g., a compact disk (CD), a digital versatile disk (DVD), amagnetic disk, a magnetic tape, and/or the like). A method and apparatusaccording to an embodiment of the present disclosure may be implementedby a computer or a mobile terminal that includes a controller and amemory, and the memory may be an example of a non-transitorymachine-readable (e.g., computer-readable), storage medium suitable tostore a program or programs including instructions for implementingvarious embodiments of the present disclosure.

The present disclosure may include a program including code forimplementing the apparatus and method as defined by the appended claims,and a non-transitory machine-readable (e.g., computer-readable), storagemedium storing the program. The program may be electronicallytransferred via any media, such as communication signals, which aretransmitted through wired and/or wireless connections, and the presentdisclosure may include their equivalents.

An apparatus according to an embodiment of the present disclosure mayreceive the program from a program providing device which is connectedto the apparatus via a wire or a wireless and store the program. Theprogram providing device may include a memory for storing instructionswhich instruct to perform a content protect method which has beenalready installed, information necessary for the content protect method,and the like, a communication unit for performing a wired or a wirelesscommunication with a graphic processing device, and a controller fortransmitting a related program to a transmitting/receiving device basedon a request of the graphic processing device or automaticallytransmitting the related program to the transmitting/receiving device.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed:
 1. A method of a user equipment (UE), the methodcomprising: receiving configuration information related to a channelstate information (CSI) process, the configuration informationcomprising configuration information of N non-zero power (NZP) channelstate information reference signal (CSI-RS) resources; and measuring achannel state based on the configuration information, wherein the CSIprocess is associated with multiple NZP CSI-RS resources, wherein the UEassumes reference physical downlink shared channel (PDSCH) transmissionpower corresponding to the multiple NZP CSI-RS resources based on atleast one parameter configured via higher layer signaling for measuringthe channel state for the CSI process based on the multiple NZP CSI-RSresources, wherein the at least one parameter includes P_(c) which is anassumed ratio of PDSCH energy per resource element (EPRE) to NZP CSI-RSEPRE, and wherein the higher layer signaling comprises the P_(c) of thereference PDSCH transmission power configured for the N NZP CSI-RSresources.
 2. The method of claim 1, further comprising: measuringinterference based on one zero power (ZP) CSI interference measurement(CSI-IM) resource.
 3. The method of claim 1, further comprising:receiving scheduling information from a base station; and receivingdownlink data based on the scheduling information.
 4. The method ofclaim 3, wherein: the scheduling information comprises information ofde-modulation reference signal (DMRS) ports allocated to the UE, anumber of data transmission layers and a number of resource element (RE)collections occupied by DMRSs, the UE receives the DMRSs based on theallocated DMRS ports and the number of data transmission layers, DMRSports 7-10 are used for supporting multi-user multiple input multipleoutput (MU-MIMO) transmission of the DMRSs, and the UE receives a PDSCHfrom an RE collection of port 9 when the DMRSs are transmitted using anRE collection of port
 7. 5. The method of claim 3, further comprising:increasing a length of a time-expanded Walsh code to support multi-usermultiple input multiple output (MU-MIMO) transmission of de-modulationreference signals (DMRSs) signals, DMRS ports having best orthogonalityamong all of DMRS ports that support MU-MIMO are allocated to differentlayers of the UE or to different UEs, wherein the scheduling informationcomprises information of DMRS ports allocated to the UE and the numberof data transmission layers.
 6. The method of claim 1, wherein measuringthe channel state comprises: measuring channel characteristics of atwo-dimensional antenna array on an axis x and an axis y respectively,wherein the axis x and the axis y are directions respectivelycorresponding to two dimensions of the two-dimensional antenna array. 7.The method of claim 6, wherein receiving the configuration informationcomprises: receiving CSI-RS signals via NZP CSI-RS ports on whichchannel characteristics on the axis x and the axis y are measured,wherein an NZP CSI-RS signal for measuring the channel characteristicson the axis x and the axis y is received from one NZP CSI-RS port for ashared antenna unit on the axis x and the axis y, and an NZP CSI-RSsignal for measuring channel characteristics of another antenna unit isreceived from the other NZP CSI-RS port for the shared antenna unit. 8.The method of claim 6, wherein antenna units in a cross-polarizedtwo-dimensional antenna array are divided into two groups according topolarization directions, wherein the configuration information comprisesconfiguration information of NZP CSI-RS ports corresponding to eachgroup of antenna units having the same polarization direction, andwherein the two groups of antenna units are configured with the samenumber of NZP CSI-RS ports.
 9. The method of claim 1, furthercomprising: reporting a pre-coding matrix indicator (PMI) andinformation of a phase between each pair of PMIs.
 10. The method ofclaim 1, wherein the P_(c) corresponds to an index k, k is the index ofeach NZP CSI-RS resource, k=0, 1, . . . N−1, and N is an integer largerthan 2, and wherein the UE assumes the reference PDSCH transmissionpower based on the P_(c) when measuring CSI based on the k^(th) NZPCSI-RS resource.
 11. The method of claim 1, wherein the UE calculatesthe reference PDSCH transmission power corresponding to a portion of themultiple NZP CSI-RS resources based on a pre-set assumption of thereference PDSCH transmission power, and wherein the channel state ismeasured based on a portion of the multiple NZP CSI-RS resources withoutusing an assumption of the reference PDSCH transmission power.
 12. Auser equipment (UE) for data processing, the UE comprising: atransceiver configured to receive configuration information related to achannel state information (CSI) process from a base station (BS), theconfiguration information comprising configuration information of Nnon-zero power (NZP) channel state information reference signal (CSI-RS)resources; and at least one processor configured to measure a channelstate based on the configuration information, wherein the CSI process isassociated with multiple NZP CSI-RS resources, wherein the UE assumesreference physical downlink shared channel (PDSCH) transmission powercorresponding to the multiple NZP CSI-RS resources based on at least oneparameter configured via higher layer signaling for measuring thechannel state for the CSI process based on the multiple NZP CSI-RSresources, wherein the at least one parameter includes P_(c) which is anassumed ratio of PDSCH energy per resource element (EPRE) to NZP CSI-RSEPRE, and wherein the higher layer signaling comprises the Pc of thereference PDSCH transmission power configured for the N NZP CSI-RSresources.
 13. The UE of claim 12, wherein the UE measures interferencebased on one zero power (ZP) CSI interference measurement (CSI-IM)resource.
 14. The UE of claim 12, further comprising: a schedulerconfigured to receive scheduling information from the base station,receives downlink data based on the scheduling information.
 15. The UEof claim 14, wherein the scheduling information comprises information ofde-modulation reference signal (DMRS) ports allocated to the UE, thenumber of data transmission layers, and wherein the UE increases thelength of a time-expanded Walsh code to support MU-MIMO transmission ofDMRS signals, and the DMRS ports having best orthogonality among all ofDMRS ports that support MU-MIMO are allocated to different layers of theUE or to different UEs.
 16. The UE of claim 12, wherein the P_(c)corresponds to an index k, k is the index of each NZP CSI-RS resource,k=0, 1, . . . N−1, and N is an integer larger than 2, and wherein the UEassumes the reference PDSCH transmission power based on P_(c) whenmeasuring CSI based on the k^(th) NZP CSI-RS resource.